Difficulties with physical functioning represented by the inability to perform routine activities of daily living are a serious problem among older adults. While considerable attention has been given to measures of the physical functioning for population-based estimates of disability, limited work has been accomplished to develop a measure that is sensitive to changes in response to specific interventions. Furthermore, no current measure of physical functioning has utilized the disablement framework as a conceptual model for evaluating changes in the physical function domain. The Specific Aims of this study are to: (1) use he disablement framework to develop a responsive measure for use in evaluating the efficiency of interventions directed toward improving physical functioning by: (a) building item scales for two levels of the disablement framework (functional limitations and disability) and (b) evaluating their scale properties; (2) estimate the intra-rater, test-retest reliability and internal consistency of the physical disablement instrument, (3) assess the validity of the instrument in relation to: (a) known-group comparisons, (b) existing measures of physical functioning, (c) predicted relationships between functional limitations and disability, and (4) determine the responsiveness of the instrument in relation to: (a) comparative instruments, and (b) independent ratings of physical functioning changes by the respondent and (c) case managers or caregivers. The final product of the study will be a conceptually grounded, responsive instrument that can be used to assess the efficacy of clinical trials directed towards minimizing the effects of functional limitations and disability. The development of this measure will be based on input from experts and consumers and constructed within the conceptual framework of the disablement process. The instrument will be field-tested with samples representing community-well community-frail and physical rehabilitation populations. Building the instrument within the disablement framework offers the advantage of describing changes in physical functioning by means of a conceptual model that hypothesizes interrelationships among factors that lead to physical disability.